Hot melt adhesive

ABSTRACT

A hot melt adhesive is disclosed consisting essentially of rubber, tackifier and liquid polybutadiene as the extenderplasticizer.

United States Patent [191 Jurrens et al.

1 Nov. 4, 1975 HOT MELT ADHESIVE Inventors: Lawrence D. Jurrens; Leo L.

Gingerich, both of Bartlesville, Okla.

Phillips Petroleum Company, Bartlesville, Okla.

Filed: June 7, 1974 Appl. N0.: 477,177

Assignee:

US. Cl 260/27 BB; 260/33.6 AQ; 260/888 Int. Cl. C08K 5/01; C08L 93/00Field of Search 260/27 R, 33.6 UA, 27 BB,

References Cited UNITED STATES PATENTS 5/1962 Arnold 260/85.1

Primary Examiner-Donald E. Czaja Assistant ExaminerH. H. FletcherABSTRACT A hot melt adhesive is disclosed consisting essentially ofrubber, tackifier and liquid polybutadiene as the extender-plasticizer.

9 Claims, No Drawings HOT MELT ADHESIVE This invention relates to theart of adhesives. More specifically, the invention relates .to hot meltadhesives consisting essentiallyof a polymer, a tackifier and anextender-plasticizer.

BACKGROUND OF. THE INVENTION THE INVENTION It is thus one object of thisinvention to provide new hot melt adhesives.

Another object of this invention is to provide new hot melt adhesiveswith improved initial tack, tack retention, and stability. 7

Further objects, aspects, advantages and embodiments of this inventionwill become apparent from. the following detailed description of theinvention and the appended claims.

In accordance with the present invention, we have discovered that theuse of a liquid polyalkadiene as the extender-plasticizer in hot meltadhesives result in an adhesive system having improved tack and tackretention properties. I

For the purposes of this invention all hydrogenated copolymers of asubstituted or unsubstituted alkadiene having 4-12 carbon atoms and asubstituted or unsubstituted vinyl-substituted aromatic monomer having8-16 carbon atoms can be used as the polymer or the rubber in the hotmelt adhesive. The preferred copolymer is a copolymer of butadiene orisoprene and styrene.

The degree of hydrogenation of the polymer preferably is such that theremaining olefmic unsaturation is less than about 3 per cent of theoriginal olefinic unsaturation. Polymers having about 1 per centoriginal olefinic unsaturation have been successfully tested in hot meltadhesives and are therefore presently preferred.

In one presently preferred embodiment of this invention there is used asthe polymer rubber a copolymer of 41 weight per cent butadiene and 59weight per cent styrene containing not more than about 20 weight percent of the total rubber in polystyrene blocks. The preparation of thisrubber is described in Example V, column 6, lines 29-50 of U.S. Pat. No.3,554,911.

For the purposes 'of this invention, any tackifier known in' the art canbe employed. Examples for such tackifiers are pentaerythritol ester ofhydrogenated rosin, e.g. Foral 85 or 105 (trade-mark) as sold byHercules Inc.; thermoplastic olefin resin, e.g. Super Sta- Tac 80(trade-mark) sold' by Reichhold Chemicals, Inc.; thermoplastichydrocarbon resins, e.g. Schenectady CRJ-683 (trade-mark) sold bySchenectady Chemical Co.; glycerol ester of hydrogenated rosin, e.g.,Staybelite Ester 1O (trade-mark) sold by Hercules Powder, Inc. Woodresins, resin esters, tackifiers of the polyterpene and the coumarineindene type could also be used. Presently preferred are thethermoplastic olefin resin tackifiers such as the product sold under thename of Super Sta-Tac 80 (trade-mark) by Reichhold Chemicals, Inc.

2 The liquid polyalkadienes useful in accordance with this invention asextender-plasticizer are liquid poly mers of alkadienes having 4-12carbon atoms per molecule. The weight average molecular weight is in therange of about 500 to about 10,000. With the exception of the C=C doublebonds such polyalkadienes are free of functional groups Wl'llCl'll mightcause crosslinking or other reactions deteriorating the desired longtermstability of the adhesive. The polyalkadienes useful in accordance withthis invention are liquid at ambient temperatures.

These polyalkadienes are prepared in conventional manners well known inthe art. The alkadiene is, for instance, polymerized in a solvent in thepresence of e.g. an alkyllithium initiator and the reaction isterminated by adding a proton donor, e.g. water, alcohol, hydrochloricacid or a fatty acid.

The preferred polyalkadienes are conjugated polyalkadienes, especiallypolybutadiene, having a weight average molecular weight of about 2,000to about 8,000 and a viscosity of about to about 125 poise at 77F.Presently most preferred is a polybutadiene having no functional groups(with the exception of the C=C double bonds) and being manufactured andsold by Phillips Petroleum Company under the trademark Butarez NF (NFstanding for nonfunctional). This polybutadiene is prepared bypolymerizing butadiene dissolved in cyclohexane in the presence ofbutyllithium as the initiator using about 10 to about 30 millimoles ofbutyllithium per 100 grams of butadiene and carrying out the reactionunder polymerization conditions and in a nitrogen atmosphere. Thereaction is terminated by adding hydrochloric acid which introduces ahydrogen instead of the lithium atom into the polymer.

The adhesives of this invention consist of a polymer, a tackifier, and apolyalkadiene. In addition, small quantities of the usual additives suchas antioxidants, stabilizers or pigments can be present in the adhesivesystem. The preferred range of components for an adhesive recipe isshown in the following table:

TABLE Ingredients Parts by weight Copolymer about 401 to about 70Tackifier about 501 to about Liquid polyalkadiene I Additives(stabilizers, pigments, antioxidants) about 101 to about 30 about I toabout 10 (optional) The preparation of the adhesives is carried out byany conventional method. For example, the ingredients are put into amixer, liquefied and blended thoroughly. The sequence of adding theingredients is not particularly critical.

The invention will be more fully understood from the following examples.

EXAMPLE I the trademark Super Sta-Tao 80 (RCl Product 47-403) werecharged and heated to about 390F. One gram of dilaurylthiodipropionate(DLTDP), 4 grams of an alkylated, arylated bis-phenolic phosphite soldunder the name of Agerite Geltrol by R. T. Vanderbilt Co., Inc. NewYork, New York and grams of mineral oil were added and the charge wasstirred for about 1 hour at 390F under nitrogen.

in the second run the same operation was carried out as in the firstrun, however instead of the mineral oil, 20 grams of a liquidpolybutadiene was used. The liquid polybutadiene was the productmanufactured and sold by Phillips Petroleum Company under the trademarkButarez NF. The liquid polybutadiene has a viscosity of 86 poise at 77F,a specific gravity of 0.8965, and a weight average molecular weight ofabout 5,000.

The adhesives thus prepared were tested to determine tack, tackretention and viscosity. The tack was measured with a Polyke n ProbeTack Tester made and sold by Testing Machines, lnc., Mineola, New Yorkimmediately after the blending was finished and for a second time afteraging the sample for 24 hours at 350F. The viscosity was measured on aBrookfield Viscosimeter using spindle No. 4-27 at 350F and 2.5 rpm,again immediately after blending and after 24 hours of aging at 350F.The results of these tests are given in Table I.

Table l Run l 2 Recipe: (parts Hydrogenated butadiene] hrs. age at 350FThe results of Table I show that both initial tack and tack retentionare considerably improved by the use of a liquid polybutadiene insteadof the usually employed mineral oil as extender-plasticizer in theadhesive formulation.

EXAMPLE II v in runs 3 and 4 of this example the operation of run 1 ofExample 1 was repeated starting from a different batch of the samerubber used in run 1 of Example I. Run 3 is a comparative run whereas inrun 4 a smaller quantity of liquid polybutadiene was employed instead ofthe mineral oil used as the extender-plasticizer in run 3. The tack wasmeasured for these samples immediately after blending; after 24, 72 andl68 hours, respectively, of aging at room temperature; and after 24, 72and 168 hours, respectively, aging at 158F. The results and recipes ofthese runs are shown in the following Table II.

Table ll Hydrogenated butadiene] styrene copolymer Super Sta-Tao 80Recipe: (parts by weight) 60 60 I Table ll-continued RunNo. 3 4

Tackifier so so Mineral Oil 20 0 Liquid polybutadiene 0 l5 DLTDP l lAgerite Geltrol 4 4 Tack (g) initial i037 1500 Test Results Tack after24-hrs.

The data of these.runs, too, show that the initial tack and tackretention are considerably improved by the invention employing theliquid polybutadiene instead of the mineral oil as theextender-plasticizer in the adhesive formulation. It is to be kept inmind that in this example only 15 parts by weight of polybutadiene havebeen employed and the results are compared with an adhesive having 20parts by weight of the mineral oil. The tack does not fall off afteraging but remains very constant for the adhesive in accordance with thisinvention. In addition the results show that there is very little changein the viscosity if liquid polybutadiene is employed in accordance withthe invention as the extender-plasticizer. A

Reasonable variations and modifications which will be apparent to thoseskilled in the art can be made in this invention without departing fromthe spirit or scope thereof.

What is claimed is: r

1. A hot melt adhesive composition consisting essentially of ahydrogenated copolymer of a substituted or unsubstituted alkadienehaving 4-12 carbon atoms and a substituted or unsubstitutedvinylsubstituted aromatic monomer having 8-16 carbon atoms per moleculewherein substantially all of the olefinic unsaturation is hydrogenated,leaving the aromatic unsaturation, a tackifier and about 10 to about 30parts by weight per about 40 to about parts by weight of the copolymerof a liquid polyalkadiene having alkadiene units of 4-12 carbon atomsper molecule, having a weight average molecular weight in the range ofabout 500 to about 10,000 and being substantially free'of otherfunctional groups than C=C double bonds.

2. A composition in accordance with claim 1 wherein the polyalkadienehas a weight average molecular weight of about 2,000 to about 8,000.

3. A composition in accordance with claim 1 wherein the alkadienemonomer of the copolymer is selected from the group consisting ofbutadiene and isoprene and the monovinyl-substituted aromatic monomer ofthe copoly meris styrene.

4. A composition in accordance with claim 3 wherein the polymer is ahydrogenated butadiene-styrene copolymer having .a butadiene content ofabout 30. to about 44 weight percent and a styrene content of about 70to about 56 weight percent.

5. A composition in accordance with claim 1 wherein the polyalkadiene ispolybutadiene.

'6. A composition in accordance with claim 5 wherein the polybutadienehas a weight average molecular weight ofrabout 5,00Qand a viscosity ofabout 75-125 poise at 77F. 7 l I 7. A hot melt adhesive compositionaccording to claim 1 wherein said tackifier is selected from the groupconsisting of pentaerythritol ester of hydrogenated rosin; thermpolasticolefin resin tackifiers, thermoplastic hydrocarbon resin tackifiers,glycerol ester of hydrogenated rosin, wood resin tackfiers, resin 'esterbilizers, pigments, and antioxidants.

1. A HOT MELT ADHESIVE COMPOSITION CONSISTING ESSENTIALLY OF AHYDROGENATED COPOLYMER OF A SUBSTITUTED OR UNSUBSTITUTED ALKADIENEHAVING 4-12 CARBON ATOMS AND A SUBSTITUTED OR UNSUBSTITUTEDVINYLSUBSTITUTED AROMATIC MONOMER HAVING 8-16 CARBON ATOMS PER MOLECULEWHEREIN SUBSTANTIALLY ALL OF THE OLEFIN UNSATURATION IS HYDROGENATED,LEAVING THE AROMATIC UNSATURATION, A TACKIFIER AND ABOUT 10 TO ABOUT 30PARTS BY WEIGHT PER ABOUT 40 TO ABOUT 70 PARTS BY WEIGHT OF THECOPOLYMER OF A LIQUID POLYALKADIENE HAVING ALKADINE UNITS OF 4-12 CARBONATOMS PER MOLECULE, HAVING A WEIGHT AVERAGE MOLECULAR WEIGHT IN THERANGE OF ABOUT 500 TO ABOUT 10,000 AND BEING SUBSTANTIALLY FREE OF OTHERFUCTIONAL GROUPS THAN C=C DOUBLE BONDS.
 2. A composition in accordancewith claim 1 wherein the polyalkadiene has a weight average molecularweight of about 2, 000 to about 8,000.
 3. A composition in accordancewith claim 1 wherein the alkadiene monomer of the copolymer is selectedfrom the group consisting of butadiene and isoprene and themonovinyl-substituted aromatic monomer of the copolymer is styrene.
 4. Acomposition in accordance with claim 3 wherein the polymer is ahydrogenated butadiene-styrene copolymer having a butadiene content ofabout 30 to about 44 weight percent and a styrene content of about 70 toabout 56 weight percent.
 5. A composition in accordance with claim 1wherein the polyalkadiene is polybutadiene.
 6. A composition inaccordance with claim 5 wherein the polybutadiene has a weight averagemolecular weight of about 5, 000 and a viscosity of about 75-125 poiseat 77*F.
 7. A hot melt adhesive composition according to claim 1 whereinsaid tackifier is selected from the group consisting of pentaerythritolester of hydrogenated rosin, thermpolastic olefin resin tackifiers,thermoplastic hydrocarbon resin tackifiers, glycerol ester ofhydrogenated rosin, wood resin tackfiers, resin ester tackifiers,polyterpene tackifiers and thermoplastic olefin resin tackifiers.
 8. Acomposition in accordance with claim 7 comprising about 40 to about 70parts by weight of said copolymer, about 50 to about 90 parts by weightof said tackifier, and about 10 to about 30 parts by weight of saidliquid polyalkadiene.
 9. A composition in accordance with claim 8comprising about 1 to about 10 parts by weight of at least one additiveselected from the group consisting of stabilizers, pigments, andantioxidants.